When light enters a fiber optic waveguide at an angle relative to a normal directional facing of a distal end of the fiber, the light is emitted from the opposite or proximal end of the fiber optic waveguide as a cone having angles of its sides that are based on the angle of incidence of the light onto the receiving end of the fiber optic waveguide. In particular, the angle of incidence of the light onto the receiving end of the fiber optic waveguide is the same as the angle at which the light exits the emitting or proximal end of the fiber optic waveguide according to the well-known principle of total internal reflection. The characteristics of the cone, such as the shape of the base of the cone projected onto a detection surface, may then be analyzed to determine the angle of incidence of the light onto the receiving end of the fiber optic waveguide. The direction and location of the light source may not be determined from a single waveguide measurement, since the direction of the light source may correspond to any point along the sides of the corresponding receiving cone from the distal end of the fiber. However, measurements from multiple fiber optic waveguides may be combined to localize and track optical sources.
In addition, if the sources are spatially fixed with respect to each other and attached to some other secondary structure, the detection system can effectively track the position and orientation of said secondary structure.
There is significant established need and prior art in the use of optical technologies and methods for localization and tracking purposes. These include interferometric techniques, such as those described in U.S. Pat. Nos. 7,515,275 and 7,349,099, the contents of which are hereby incorporated by reference in their entirety, as well as numerous methods based on triangulation, imaging, both monoscopic and stereoscopic, position sensitive detectors (PSDs), and active laser ranging methods based on time of flight measurements. However, fiber optic sensors have not typically or commonly been used for localization and tracking. In some cases, localization and tracking using fiber optic sensors has distinct advantages over other tracking methods. For instance, in some cases, the sensing head of the tracking system must be low profile and must be able withstand high temperatures or other extreme environmental conditions that would preclude the use of imagers or other direct sensing components such as PSDs.
U.S. Patent application No. 2009/0314925 (Van Vorhis et al.), Fiber Optic Tracking System and Method for Tracking, which is hereby incorporated by reference in its entirety, describes a method for tracking an object by processing the signal from an optical fiber that is attached to the tracked object.
U.S. Pat. No. 7,071,460 (Rush), Optical Non-Contact Measuring Probe, which is hereby incorporated by reference in its entirety, describes an active sensor that emits an optical signal towards a proximate surface and then couples the reflected signal back into an optical fiber. The light pattern exiting the proximal end of the fiber is analyzed to compute the displacement to the reflective surface. This active sensor is intended for use in restricted spaces for very small displacements over a range of a few millimeters.
U.S. Pat. No. 6,792,185 (Ahrens, et al.), Method and Apparatus for Automatic Tracking of an Optical Signal in a Wireless Optical Communication System, which is hereby incorporated by reference in its entirety, describes a method, using a fiber optic bundle, to maintain directional coupling to a communications signal by comparing the amplitudes of the signals from various fibers in the array to generate a feedback signal to adjust the orientation of the receiving unit.
U.S. Pat. No. 5,196,714 (Garcia, Jr., et al.), System for X-Y Alignment and Tracking of Moving Targets Having Angular Displacement with Fiber Optic Sensing Surface, which is hereby incorporated by reference in its entirety, describes a fiber optic system and method for tracking a source, based on triangulation, and using row and column arrays of fibers.
U.S. Pat. No. 5,085,507 (Williams, et al.), Device for Three Dimensional Tracking of an Object, which is hereby incorporated by reference in its entirety, also uses column and row arrays of fiber optic sensors to determine the position of a source.